How I built a 2.8TB RAID storage array

My 2.8TB RAID 5 array is finally up and running. Here I'll discuss my
initial intended specifications, what I actually ended up with, and
associated commentary. Please see
URL:http://groups.google.ca/groups?selm=slrnch28at.j0n.ylee%40pobox.com
and
URL:http://groups.google.ca/groups?selm=slrncu34ip.55k.ylee%40pobox.com
for background material.

STORAGE MEDIUM
Initial: Eight 250GB SATA drives.
Actual: Nine 400GB PATA drives; eight for use, one as a cold spare.
Why: Found a stupendous sale at CompUSA Christmas week;
just-released-in-November Seagate Barracuda 7200.8 400GB PATA drives
at $230 each, with no quantity limitation . I'd have loved to have
gone with the SATA model, but given that Froogle lists the lowest
price for one at $350 (the PATA model retails at $250-350), it was an
easy choice.


CASE
Initial: Antec tower case.
Actual: Antec 4U rackmount case.
Why: I'd always thought of rackmounts as unsuitable for anyone with an
actual rack sitting in their data center, but after realizing that a
rackmount case is simply a tower case sitting on its size, it was an
easy decision given the space advantages. The Antec case here comes
with Antec's True Power 550W EPS12V power supply, and both have great
reputations. In practice, I found that the Antec case was remarkably
easy to open up (one thumbscrew), work with (all drive cages are
removable), and roomy.


MOTHERBOARD
Initial: Unspecified, but probably something Athlon-based and cheap.
Actual: Gigabyte X5DAL-G Intel server motherboard
Why: I became convinced that the sheer volume of the PCI traffic
generated by my proposed array under software RAID would overwhelm any
non-server motherboard, resulting in errors. In addition, I wanted
PCI-X slots for optimal performance. Even though I think AMD in
general offers much better bang for the buck, since I didn't want to
spend the $$$ for Opteron, a Xeon motherboard with an Intel server
chipset was the best comprimise.


CONTROLLER CARDS
Initial: Two Highpoint RocketRAID 454 cards.
Actual: Two 3Ware 7506-4LP cards.
Why: I needed PATA cards to go with my PATA drives, and also wanted to
put the two PCI-X slots on my motherboard to use. I found exactly two
PATA PCI-X controller cards: The 3Ware, and the Acard AEC-6897. Given
that the Acard's Linux driver compatibility looked really, really
iffy, I went with the 3Ware. I briefly considered the 7506-8 model,
which would've saved me about $120, but figured I'd be better off
distributing the bandwidth over two PCI-X slots rather than one.


SOFTWARE
Initial: Linux software RAID 5 and XFS or JFS.
Actual: Linux software RAID 5 and JFS.
Why: Initially I planned on software RAID knowing that the Highpoint
(and the equivalent Promise and Adaptec cards) didn't do true hardware
RAID. Even after switching over to 3Ware (which *does* do true
hardware RAID), everything I saw and read convinced me that software
RAID was still the way to go for performance, long-term compatibility,
and even 400GB extra space (given I'd be building one large RAID 5
array instead of two smaller ones).

I saw *lots* of conflicting benchmarks on whether XFS or JFS was the
way to go. Ultimately
URL:http://pcbunn.cacr.caltech.edu/gae/3ware_raid_tests.htm pushed
me toward JFS, but I suspect I could have gone XFS with no difficulty
whatsoever.


COST
As implied above, I paid $2070 plus sales tax for the drives. I lucked
out and found a terrific eBay deal for a prebuilt system containing
the above-mentioned case and motherboard, two Xeon 2.8GHz CPUs, a DVD
drive, and 2GB memory for $1260 including shipping labor aside, I'd
have paid *much* more to build an equivalent system myself. The 3Ware
cards were $240 each, no shipping or tax, from Monarch Computer. With
miscellaneous costs (such as a Cooler Master 4-in-3 drive cage and an
80GB boot drive from Best Buy for $40 after rebates), I paid under
$4100, tax and shipping included, for everything. At $1.46/GB *plus* a
powerful dual-CPU system, boatloads of memory, and a spare drive, I am
quite satisfied with the overall bang for the buck.


ASSEMBLY: HARDWARE
I spent most of the assembly time on the physical assembly part; it's
astonishing just how long the simple tasks of opening up each
retail-boxed drive, screwing the drive into the drive cage, putting
the cage into the case, removing the cage and the drive when you
realize you've put the drive in with the wrong mounting holes,
reinstalling the drive and cage, etc., etc. take! My studio apartment
still looks like a computer store exploded inside it.

3Ware wisely provides PATA master-only cables with its cards, which
saved some room, but my formerly-roomy case nonetheless looks like the
rat's nest to end all rat's nests inside.


ASSEMBLY: SOFTWARE
I'd gone ahead and installed Fedora Core 3 with the boot drive only
before the controller cards arrived. The 3Ware cards present each
PATA drive as a SCSI device (/dev/sd[a-h]). Once booted, I used mdadm
to create the RAID array (no partitions; just whole drives). While the
array chugged along to create the parity information (about four
hours), I then created one large LVM2 volume group and logical volume
on top of the array, then created one large JFS file system.

By the way, I found a RAID-related bug with Fedora Core's bootscripts;
see URL:https://bugzilla.redhat.com/beta/show_bug.cgi?id=129633).


RESULTS
'df -h':
/dev/mapper/VolGroup01-LogVol00
2.6T 221G 2.4T 9% /mnt/newspace


'mdadm --detail /dev/md0':
Version : 00.90.01
Creation Time : Wed Feb 16 01:53:33 2005
Raid Level : raid5
Array Size : 2734979072 (2608.28 GiB 2800.62 GB)
Device Size : 390711296 (372.61 GiB 400.09 GB)
Raid Devices : 8
Total Devices : 8
Preferred Minor : 0
Persistence : Superblock is persistent

Update Time : Sat Feb 19 16:26:34 2005
State : clean
Active Devices : 8
Working Devices : 8
Failed Devices : 0
Spare Devices : 0

Layout : left-symmetric
Chunk Size : 512K

Number Major Minor RaidDevice State
0 8 0 0 active sync /dev/sda
1 8 16 1 active sync /dev/sdb
2 8 32 2 active sync /dev/sdc
3 8 48 3 active sync /dev/sdd
4 8 64 4 active sync /dev/sde
5 8 80 5 active sync /dev/sdf
6 8 96 6 active sync /dev/sdg
7 8 112 7 active sync /dev/sdh
Events : 0.319006


'bonnie++ -s 4G -m 3ware-swraid5-type -p 3 ; \
bonnie++ -s 4G -m 3ware-swraid5-type-c1 -y & \
bonnie++ -s 4G -m 3ware-swraid5-type-c2 -y & \
bonnie++ -s 4G -m 3ware-swraid5-type-c3 -y &'
(To be honest these results are just a bunch of numbers to me, so any
interpretations of them are welcome. I should mention that these were
done with three distributed computing [BOINC, mprime, and
Folding@Home] projects running in the background. Although 'nice -n
19' each, they surely impacted CPU and perhaps disk performance
somewhat.)

Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
3ware-swraid5-ty 4G 15749 50 15897 8 7791 6 10431 49 20245 11 138.1 2
------Sequential Create------ --------Random Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
16 381 6 +++++ +++ 208 3 165 7 +++++ +++ 192 4
3ware-swraid5-type-c1,4G,15749,50,15897,8,7791,6,10431,49,20245,11,13 8.1,2,16,381,6,+++++,+++,208,3,165,7,+++++,+++,192 ,4
done.
Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
3ware-swraid5-ty 4G 13739 46 17265 9 7930 6 10569 50 20196 11 146.7 2
------Sequential Create------ --------Random Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
16 383 7 +++++ +++ 207 3 162 7 +++++ +++ 191 4
3ware-swraid5-type-c2,4G,13739,46,17265,9,7930,6,10569,50,20196,11,14 6.7,2,16,383,7,+++++,+++,207,3,162,7,+++++,+++,191 ,4
done.
Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
3ware-swraid5-ty 4G 13288 43 16143 8 7863 6 10695 50 20231 12 149.6 2
------Sequential Create------ --------Random Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
16 537 9 +++++ +++ 207 3 161 7 +++++ +++ 188 4
3ware-swraid5-type-c3,4G,13288,43,16143,8,7863,6,10695,50,20231,12,14 9.6,2,16,537,9,+++++,+++,207,3,161,7,+++++,+++,188 ,4


FINAL NOTES, THOUGHTS, AND QUESTIONS
I've noticed that over sync NFS, initiating a file copy from my older
Athlon 1.4GHz system to the RAID array system is *much, much, much*
(seconds as opposed to many minutes)slower than if I initiate the copy
in the same direction but from the array system. Why is this?

I almost went with the SATA (8506) version of the 3Ware cards and a
bunch of PATA-SATA adapters in order to maintain compatibility with
future drives, likely to be SATA only. However, a colleague pointed
out the foolishness of paying $200 extra ($120 for eight adapters plus
$80 for the extra cost of the SATA cards) in order to (possibly)
futureproof a $480 investment.

I was concerned that the drives (and the PATA cables) would cause
horrible heat and noise issues. These, surprisingly, didn't occur;
according to 'sensors', internal temperatures only rose by a few
degrees, and the server is just as (very) noisy now as pre-RAID
drives. I think I'l be able to get away with stuffing the array inside
my hall closet after all.

The server, before I put the cards and RAID drives into the system but
with the distributed-computing projects putting the CPU at 100%
utilization, took the power output on my Best Fortress 750VA/450W UPS
from about 55% to about 76%. With the RAID up and running and again
with 100% CPU utilization, output is 87-101% with the median at
perhaps 93%. I realize I really ought to invest in another UPS, but
with these figures I'm tempted to get by on what I currently have.

Yes, I could've saved a considerable amount of money had I gone with,
say, a used dual PIII server system with regular PCI slots (and, thus,
$80 Highpoint RAID cards, again for the four PATA channels and not for
their RAID functionality per se) and 512MB. And I suspect that for a
home user like me performance wouldn't have been too much less. But I
like to buy and build systems I can use for years and years without
having to bother with upgrading, and figure I've made a long-term (at
least 4-5 years, which is long term in the computer world) investment
that provides me with much more than just storage functionality. And
again, $1.46/GB is hard to beat.

--
Read my Deep Thoughts @ URL:http://www.ylee.org/blog/ PERTH ---- *
Cpu(s): 6.7% us, 3.7% sy, 0.4% ni, 75.4% id, 12.3% wa, 1.4% hi, 0.0% si
Mem: 515800k total, 511628k used, 4172k free, 5812k buffers
Swap: 2101032k total, 13152k used, 2087880k free, 163928k cache